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Build­ing for the future with self-repair­ing concrete

08.06.2015
One of the team, Elke Gruyaert, explained the pro­cess: ​“The con­crete is filled with super-absorb­ent poly­mers. So when a crack appears, water comes in, and the super-absorb­ent poly­mers swell and they block the crack from fur­ther intake of water.” The poly­mers are added to the con­crete mix. Once it is dry, the research­ers crack it to see how it reacts. Then they quanti­fy its mech­an­ic­al beha­viour, imper­meab­il­ity and dur­ab­il­ity. Brenda Debbaut, an indus­tri­al engin­eer at Ghent Uni­ver­sity, says the res­ults are very quickly evid­ent: ​“If a small crack starts heal­ing imme­di­ately, then there is no risk that it grows big­ger. So the total struc­ture won’t run the risk of fall­ing down. We want to stop the prob­lem before it is big enough”. Sci­ent­ists work­ing on the European-backed research pro­ject think these elast­ic poly­mers can indeed pro­tect struc­tures bear­ing dynam­ic and mech­an­ic­al loads. In bridges and tun­nels even tiny cracks turn into poten­tially dan­ger­ous dam­age. Nele de Belie, Tech­nic­al Dir­ect­or of the Mag­nel Labor­at­ory for Con­crete Research says imper­meab­il­ity is the key factor: ​“You do not have healed con­crete regain its strength com­pletely. It’s strong enough as it is. What you do want to regain is the liquid tight­ness and imper­meab­il­ity, so that dur­ab­il­ity still remains fine”. There are oth­er bio­lo­gic­al products that can be used to help con­crete repair itself. At Delft Uni­ver­sity of Tech­no­logy in the Neth­er­lands, research­ers have iden­ti­fied anoth­er agent to help con­crete self-heal – bac­teria. ​“These are bac­teria that we have isol­ated from loc­a­tions in our plan­et that have con­di­tions which are sim­il­ar to con­crete,” says Henk Jonkers, a bio­lo­gist at Delft Uni­ver­sity of Tech­no­logy. ​“One con­di­tion is rock-like. The oth­er con­di­tion is being very alkaline, so very high pH con­di­tions. These bac­teria like to grow under those con­di­tions. These bac­teria are not patho­gen­ic, and are not harm­ful for human beings or for the envir­on­ment”. As soon as a small crack appears, bac­teria con­tained with­in the con­crete mixes with leaked water, cre­at­ing cal­ci­um car­bon­ate that seals the crack. Research­ers are cur­rently test­ing how imper­meable the bac­teria-driv­en seal­ing really is. ​“We are try­ing to see if the liquid can pen­et­rate through our healed crack, by how much, and what is is the dif­fer­ence before heal­ing and after heal­ing,” says Eirini Tzivilo­glou, anoth­er civil engin­eer at Delft Uni­ver­sity of Tech­no­logy. Sci­ent­ists now aim to imple­ment the tech­no­logy in real struc­tures. With around 70% of European tun­nels and bridges made of con­crete, they say these heal­ing agents have sig­ni­fic­ant mar­ket poten­tial, as Nele de Belie explains: ​“The ini­tial cost will increase. But then if you can reduce the main­ten­ance costs and you increase the ser­vice life of the struc­tures, then at the end, this self-heal­ing con­crete presents an eco­nom­ic­ally pos­it­ive pic­ture”. More tests are needed but self-heal­ing con­crete could become a viable product on the mar­ket.

Pro­ject details

  • Pro­ject acronym: HEALCON
  • Par­ti­cipants: Bel­gi­um (Coordin­at­or), Ger­many, Neth­er­lands, Fin­land, Spain, Den­mark, Portugal
  • Pro­ject Ref­er­ence: N° 309451
  • Total cost: €5 610 518,8
  • EU con­tri­bu­tion: €3 997 429
  • Dur­a­tion: Janu­ary 2013 — Decem­ber 2016
Source: European Commission
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